Art of making shoe stiffeners



Patented Jan. 31, 1933 UNITED STATES DAVID BAIRD MACDONALD, OF LEICESTER, ENGLAND, ASSIGNOR 'I'O UNITED SHOE MACHINERY CORPORATION, OF PATERSON, NEW JERSEY, A CORPORATION OF JERSEY NEW ART OF MAKING SHOE STIFFENERS No Drawing. Application filed April 27, 1931, Serial No. 533,373, and in Great Britain May 24, 1930.

This invention relates to methods of manufacturing stiffener blanks for use in boots and shoes and more particularly to methods of manufacturing and packaging toe stiffener blanks which are limp and plastic when they are inserted in the uppers of shoes, due to the presence in them of a stiffening substance maintained soft by a volatile solvent which is later permitted to evaporate.

Toe stiffener blanks of this general type usually comprise a fibrous base, which maybe a textile fabric, impregnated or coated with a stiffening substance, which is commonly celluloid or a mixture of celluloid and one or more resins. Such toe stiffener blanks, with the stiffening substance properly soft by reason of the presence in the blank of a solvent for the stiffening substance, are placed in the uppers of shoes prior to the lasting operation by which they are conformed, with part of the upper, to the toe portion of the last. As soon as the solvent has evaporated, the blank becomes stiff and resilient.

There are two commonly employed methods of making such stiffener blanks. According to one method, a piece of sheet material is impregnated with a stiffening substance in solution, and the limp and plastic sheet is then allowed to dry. The blanks are subsequently cut out of this sheet material and remain dry and stiff while they are first skived and later packed in bundles. Such stiffener blanks require to be dipped in asolvent ust prior to placing them in the uppers of shoes. According to another method, the fabric bases are cut out of a sheet of untreated fabric, and are subsequently coated or impregnated. Thereafter the limp and plastic blanks are not dried but remain in their limp and plastic condition while they are skived and packed in airtight containers. Such stiffener blanks require no further treatment before they are placed in the uppers of shoes.

The present invention relates to improvements in the second and similar methods in which impregnated stiffener blanks remain limp and plastic while they are being operated upon or otherwise handled. There will be described the manufacture of stiffener blanks impregnated with a solution of celluloid, the terms solvent and solution being used in a general sense as embracing respectively swelling or dispersing agents for colloids and the condition attained by the use of such agents.

When a toe stiffener blank has been treated with a solution of a stiffening substance, it is not only limp and plastic but also sticky; and this stickiness greatly interferes with operating upon and handling the blanks, for example, with skiving them and storing them in air-tight cans or containers. I have found that in such case the sticky blanks may be subjected to a treatment which causes the solvent effect of the solvent present to be temporarily reduced, at all events at and near the surfaces of the blanks, so that the limp and plastic blanks become substantially nonsticky. This non-sticky condition remains as long as the effect of this treatment is caused to persist, the solvent present in the blanks being temporarily prevented from exercising upon the stiffening substance the solvent capacity which it will ultimately exercise prior to the final drying of the blank in the finished shoe.

I Various applications of the invention will now be described involving the impregnating of already cut out fabric bases with a stiffening substance in solution. The bases may be heavilycharged with a stiffening substance in solution by any suitable apparatus, for example by that shown in British Patent No. 340,603 in which a pair of belts, having runs which contact simultaneously with both faces of the blanks, apply to said faces a thick, celluloid solution. The solvent used consists largely of a liquid of high volatility, such as acetone, or of a mixture of such liquids, for example,.acetone and ethyl alcohol, together with a less amount of a solvent of low volatility, such as diacetone alcohol, the purpose of which will be explained hereafter. The sticky, impregnated blanks, on leavin the impregnating apparatus, may be passed through a bath of a restraining liquid which is miscible with the solvent but is of itself substantially a non-solvent of the stiffening substance, or through a chamber containing vapor of such a liquid. Peferably water will In this condition they may then be skived on a skiving machine of usual construction, for example, upon any of the-well-known machines having rotating cylindrical knives. The skived, limp and non-sticky blanks may then be stored in containers which are sealed so as to be air tight; and these containers may be shipped to shoe factories.

When the user at the shoe factory opens the sealed container in which he has received the blanks, he has merely to remove the limp blanks one by one, place them in the uppers of shoes just prior to the lasting operation and proceed as usual with the manufacture of the shoe. Such solvent and water as have re mained in the blank after the lasting operation are allowed to evaporate while the shoe is on the last. The solvent of low volatility, such as diacetone alcohol, remains in the blank until after all the other liquids have evaporated; and, before it finally evaporates, imparts to the blank a certain measure of stickiness. This stickiness, together with the tensions resulting from the lasting operation which squeeze the upper, the blank and the lining together, causes an intimate union of the parts of the shoe at the toe portion; and the stiffening substance finally dries out in its stiff, resilient form, thereby imparting the desired qualities to the toe portion of the shoe.

It is advantageous in some circumstances to coat the sticky blanks on one or both faces with a finely divided substance such as wood meal. For example, if the sticky blanks are to be treated with water or other vapor to render them non-sticky, a coating of wood meal applied to the sticky face or faces ap-' pears to assist the vapor in wetting the blanks. Again, the sticky blanks, after having been exposed to a water bath and then pressed to expel excess liquid and to compact them, as described above, may at some time before they are stored in the containers, be coated with a thin layer of wood meal. In such case this finely divided absorbent substance apparently draws the solution of stiffening substance to the surface during the drying of the blanks in the finished shoes and thus speeds up the drying operation.

Although, in order to promote brevity, the stifi'ening substance has been assumed to be celluloid, the solvent to be a mixture of acetone and diacetone alcohol and the restraining liquid, which reduces the stickiness, to be water, it should be understood that other substances may be used. As to the stiffening substance, pyroxylin or other esters of cellulose, resins or mixtures of resins with the other substances named, may be used. In place of acetone, various solvents of high volatility may be used depending somewhat upon the composition of the stiffening substance. Commonly used solvents are acetone alone or mixed with ethyl alcohol, and mixtures of alcohol and ether. Suitable solvents of low volatility, in addition to the diacetone alcohol mentioned above, are secondary butyl acetate and amyl acetate. \Vater has been chosen for use as a restraining agent to reduce the stickiness; but other liquids, such as gasoline, which are miscible with the solvent and have no substantial solvent capacity for the stiffening substance, may be employed.

s described above, the solvent for the stiffening substance comprised a mixture of liquids, one of which (diacetone alcohol) was a liquid of low volatility, the purpose of which was to exert, in the final drying of the blank in the finished shoe, a redissolvin action upon that portion of the celluloid, w iich was presumably precipitated by the prior treatment with water so that the celluloid should finally dry out in a hard, resilient, non-precipitated form. It has been found, however, that the employment of-a solvent of low volatility in the manner described can be dispensed with. I have found that an impregnated sticky blank may be rendered temporarily non-sticky at and near the surface thereof by employing as the solvent a mixture of liquids comprising a solvent, such as acetone, and a so-called'diluent, such as benzol, which is miscible with 'the solvent but not with water and has no substantial solventcapacity for the stiffening substance, such as celluloid. A sticky blank impregnated with such a solution, wet with water or water vapor so as to render it non-sticky at and near its surface, pressed, skived and stored in the manner described above, may be used in making a shoe. In such case the benzol or other liquid which is not miscible with water acts usefully in some way in the final drying out of the blank in the shoe so that after all of the water has evaporated, there still remains enough acetone to ensure that any celluloid which was previously partly precipitated by the water shall be redissolved so that the blank in its final form shall be still and resilient. I am unable to explain exactly what occurs. It seems possible, however, that the benzol or other equivalent liquid protects a quota of the acetone by reason of its avidity or acetone and its repulsion for water, so that sufficient solvent remains occluded in the body of the blank, as the water dries out ICS from the surface of the blank, to exercise a redissolving action upon the celluloid just prior to the final step in the drying of the stiffener in the shoe.

In such a case as that last described, it may be advantageous, before the stiffener blanks are stored in the air-tight containers, to give them a surface dressing with a solvent of low volatility, such as diacetone alcohol. When the stiffener blank has been incorporated in the shoe the solvent of low volatility assists in developing in the non-sticky surfaces of the blank a certain stickiness as the blank dries which helps to bond the blank to the adjacent layers of the shoe.

Having thus described the invention, what I claim as new and desire to secure by Letters Patent ofthe United States is:

1. The method of making shoe stiffener blanks which comprises treatin a fabric base with a stiflemng substance 1n solution inavolatile solvent whereby a limp and sticky blank results, treating the limp and sticky blank with'a non-solvent for the stiffening substance which is miscible with the solvent to reduce the stickiness of the blank, and o crating upon the blank in its limp and so stantially non-sticky condition.

2. The method of making shoe stiffener blanks which comprises treating a fabric base with a stiffening substance in solution in a volatile solvent whereby a limp and sticky blank results, treating the limp and sticky blank with a non-solvent for the stiffening substance, which ismiscible with the solvent to reduce the stickiness of the blank, and skiving the blank in its limp and substantially non-sticky condition.

3. The method of making shoe stiffener blanks which comprises treating a fabric base with a stiffening substance in solution in a volatile solvent whereby a limp and sticky .blank results, treating the limp and sticky blank with a non-solvent for the stiffening substance which is miscible with the solvent to reduce the stickiness of the blank, skiving the limp and substantially non-sticky blank, and storing it in an air-tight container.

4. The method of making shoe stiffener blanks which comprises treating a fabric base with a stiffening substance in solution in a volatile solvent whereby a limp and sticky blank results, treating the blank with a liquid which is less volatile than the solvent, is miscible with the solvent, and is substantially a non-solvent for the stiffening substance to reduce the stickiness of the blank while maintaining the limpness, and operatlng upon the blank in its limp, substantially nonsticky condition.

5. The method of making shoe stiffener blanks which comprises treating a fabric base with a stiffening substance in solution in a volatile solvent whereby a lim and sticky blank results, treating the bla with a liquid which is less volatile than the solvent, is miscible with the solvent, and is substantially a non-solvent for the stiffening substance to reduce the stickiness of the blank while maintaining the limpness, and skivmgthe blank in its limp, substantially non-sticky condition.

6. The method of making shoe stiffener blanks which comprises treating a fabric base with a stiffening substance in solution in a volatile solvent whereby a limp and sticky blank results, coating the blank on one or both faces with a finely divided absorbent substance, treating the blank with the vapor of a liquid which is substantially a non-solvent for the stiffening substance and is miscible with the solvent to reduce the stickiness, and operating upon the blank in its limp and substantially non-sticky condition.

7. The method of making shoe stifi'ener blanks which comprises treating a fabric base with a stiffening substance in solution in a volatile solvent whereby a limp and sticky blank results, coating the blank on one or both faces with a finely divided absorbent substance, treating the blank with the vapor of a liquid which is substantially a non-solvent for the stilfening substance and is miscible with the solvent to reduce the stickiness, skiving the limp and substantially non-sticky blank, and storing it in an air-tight container.

8. Themethod of making shoe stiffener blanks which comprises'trcating a fabric base with a stiffening substance which includes an ester of cellulose in solution in a liquid which is miscible with water and includes a solvent of higher volatility than that of water and a solvent of lower volatility than that of water whereby a limp and sticky blank results, treating the limp and sticky blank with water to precipitate the stiffening substance at and adjacent to the surface of the blank and thereby to reduce the stickiness of the blank, skiving the limp and substantially non-sticky blank, and storing it in a container. I

9. The method of making shoe stiffeners which comprises treating a fabric base with a colloidal stiffening substance in solution in a liquid which includes a solvent of high volatility whereby a limp and sticky blank results, treatin the limp and sticky blank with a restraining liquid which has a lower volatility than that of the high volatility solvent, is miscible with the solvent, and has no substantial solvent capacity for the stiffening substance whereby the stickiness of the blank is reduced, skiving the limp and substantially non-sticky blank, storing the blank in a container, and, at some time prior to the storing, introducing into the blank a solvent which has a lower volatility than that of the restraining liquid.

10. The method of making stifl'ener blanks which comprises treating a fabric base with a colloidal stiffening substance in solution in a mixture of liquids which includes a solvent of high volatility and a diluent whereby a limp and sticky blank results, treating the blank with a restraining liquid which is miscible with the solvent but not with the diluent to reduce the stickiness of the blank, and operating upon the limp and substantially non-sticky blank.

11. The method of making stifiener blanks which comprises treating a fabric base with a colloidal stiffening substance in solution in a mixture of liquids which includes a solvent of high volatility and a diluent whereby a limp and sticky blank results, treating the blank with a restraining liquid which is miscible with the solvent but not with the diluent to reduce the stickiness of the blank, operating upon the limp and substantially nonsticky blank, storing it in a container, and, at some stage prior to the storing, introducing into the blank a solvent for the stiffening substance which has a lower volatility than that of the restraining liquid.

12. 'l. he method of treating a limp and sticky blank containing a stiffening substance in solution in a volatile solvent which comprises precipitating the stiffening substance at and adjacent to the surface of the blank to render the blank substantially non-sticky, and skiving the blank in its limp and nonsticky condition.

13. The method of treating a limp and sticky St'lliCIlQI blank containing a stiffening substance in solution in a volatile solvent which comprises treating the limp and sticky blank with a substance which is substantial- 1y a non-solvent for the stiffening substance and is miscible with the solvent to reduce the stickiness, and reducing the thickness of an edge of the limp and substantially nonsticky blank.

1- The method of treating a limp and sticky blank containing a cellulose ester in solution which comprises treating the blank with a substance which is miscible with the solvent for the cellulose ester but is substan tially a non-solvent for the cellulose ester whereby the stickiness of the blank is re duccd, and skiving the limp and substantially non-sticky blank.

In testimony whereof I have signed my name to this specification.

DAVID BAIRD MACDONALD. 

